Modified polybutylene-based hot melt compositions

ABSTRACT

A hot melt adhesive and a laminar structure fabricated from a blend comprising a modified or unmodified ethylenic copolymer, a modified or unmodified butene-1 homopolymer or copolymer, a stabilizer and one or more of: a tackifying resin compatible with the major amount of modified polymer, a wax, and atactic polypropylene.

This is a continuation-in-part of U.S. Ser. No. 091,484, filed Aug. 31,1987, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a hot melt adhesive capable of forminga peelable adhesive bond and which is substantially composed of modifiedbutene-1 homopolymer or copolymer or a modified ethylene homopolymer orcopolymer. It is anticipated that this hot melt adhesive will be capableof exhibiting good polymer to polymer bonding. The present inventionalso relates to a laminar structure formed with the novel hot meltadhesive capable of forming peelable seals.

Hot melt adhesives can be formulated to be pressure sensitive but theseadhesives are usually soft, tacky and have limited strength andadhesion. Conventional hot melts such as formulations of ethylenevinylacetate copolymer (EVA), polyethylenes (PE), polyamides, or polyestersare rigid, and form good strong bonds to certain substrates and aregenerally incapable of being peelable.

Solvent applied contact adhesives provide good bond strengths but theyrequire the use of solvents which can be either toxic, or pollutants orfire hazards. Further, few of these adhesives are capable of"peelability" as the term is later defined.

The novel polybutylene hot melt adhesive of the present invention isunique in that it requires no solvents, and has peelability, and iscapable of bonding to a variety substrates.

A "peelable seal or bond" or a seal or bond having "peelability" isdefined to be the seal or joint between two films or other types ofsubstrates produced by either, heat sealing, impulse sealing, orapplication as a hot melt between two surfaces with the joint thusformed being able to be opened in the original plane joining the twofilms, by the action of a pulling force, without the opening of thejoint causing wrenching off or tearing in the substrate(s) and thematerial from which the two films of the joint are made. For thepurposes of the present invention, the peelable seal or bond mustpossess a mechanical resistance to opening or "peeling" which issufficient to maintain a tight seal around an item or quantity of liquidor solid during storage and transport until a user of the packagedarticle wants access to the contents of the sealed packaging. Themechanical resistance of the peelable seal must be low enough to permitready manual opening of the joint, i.e., without the use of an auxiliaryinstrument to break the joint.

The term "peelability" in this application refers to the sealed area ofthe adhesive where the adhesive is joined to a substrate. The adhesivepeelability is measured by the degree of strength applied. Such hot meltadhesive peelability can be measured by ASTM testing method D-1876,(T-Peel test) for 180° peelability and alternatively by ASTM testingmethod D-903 for 180° peelability.

The invention relates to blends and a method for making a blend usableas a hot melt adhesive in a packaging application. This inventionrelates to laminates prepared with these hot melt adhesives and whichare characterized by a nearly constant peel strength over an extendedheat seal or application temperature. The blends, films and/or laminatesof the present invention permit the manufacture of a more consistentfinished product, having a seal of predictable and constant peelstrength, in spite of inevitable variations in the heat sealtemperatures or application temperature used in the production of suchpackages.

In the past, many varieties of thermoplastic materials have beenemployed in the manufacture of films capable of forming peelable seals.See, for example, U.S. Pat. No. 4,189,519, to American Can, whichdiscloses a blend for producing a peelable heat seal comprising (1)about 50 to 90 percent by weight of a copolymer of about 80 to 96percent by weight ethylene and about 4 to 20 percent by weight of anethylenically unsaturated ester, and (2) about 10 to 50 percent byweight of a crystalline isotactic polybutylene. While capable of forminga peel seal, the film of the '519 patent comprises polybutylene as aminor component. The blend of '519 bonds to high density polyethylene(HDPE) without the use of adhesive, and will not bond to polypropylenewithout an adhesive.

U.S. Pat. No. 3,900,534 to Mobil Oil Corporation discloses thermoplasticshrink films with good heat seal characteristics and good opticalproperties, however, '534 does not address the need for a peel sealfilm.

U.S. Pat. No. 3,879,492 to UCB S.A. Belgium discloses blends consistingof polybutylene, styrene-butadiene copolymer, low density polyethylene,high density polyethylene, and polyisobutylene.

U.S. Pat. No. 4,539,263 to E.I. DuPont de Nemours & Co. discloses peelseals based on propylene/α-olefin copolymer. U.S. Pat. No. '263 does notappear to provide disclosure directed toward polybutylene polymers.

U.S. Pat. Nos. 4,665,130 and 4,666,778 disclose blends of polybutyleneand EVA (or polyethylene) and polypropylene with the polypropylene beingless than 15 weight percent in the blend. However, none of thesereferences teaches the novel invention.

U.S. Pat. No. 3,573,240 describes hot melt adhesive compositions forhard cover book binding. At column 4, lines 1 through 7, '240 teachesthat minor amounts i.e., up to about 5% by weight of alpha olefincomonomers such as ethylene and propylene may be present in the butene-1polymerization system without any substantial loss of the desirableproperties displayed by the resultant, essentially homopolymeric system.The '240 patent also recites, in column 2, lines 61 through 63, that thebook binding hot melt adhesives display good heat stability and rapidsetting speeds. The '240 patent does not disclose a peelable hot meltadhesive, even though up to about 5% by weight of ethylene may be addedto a substantially butene-1 polymerization system. Thus, '240 is inopposite from the teachings of the present invention which describes theuse of a blend of an ethylene homopolymer or copolymer with a modifiedbutene-1 homopolymer or copolymer to form a peelable bond.

Other patents of interest include U.S. Pat. No. 4,198,327 to Matsumotowhich describes a composition having improved adhesion that is made upof a Component A (which is 70 to 99 parts of a crystalline polyolefinwhich has been grafted with a monomer selected from the group consistingof unsaturated carboxylic acids and their anhydrides, esters, amideimides, and metal salts with the grafting monomer in an amount of 0.0001to 3% by weight) and a second Component (B) which is 1 to 30 parts byweight of a hydrocarbon elastomer wherein the hydrocarbon elastomer iseither ethylene/propylene rubber, ethylene-1-butene rubber, butylrubber, butadiene rubber, sytrene/butadiene rubber, ethylene/butadienerubber, or isoprene rubber.

Also of interest are two patents issued to Inoue, U.S. Pat. Nos.4,619,972 and 4,440,911. U.S. Pat. No. '972 describes a modified polymercomposition comprising elastomers blended with not more than 50 parts byweight of a crystalline polyolefin that is prepared by reaction of thepolymer with an unsaturated carboxylic acid or its acid anhydride. Theelastomers of this patent include ethylene/butene-1 copolymer,ethylene/propylene copolymer, a styrene/butadiene copolymer or mixturesthereof. The crystalline polyolefin of this invention includeshomopolymers of olefins or copolymers of different kinds of olefins suchas high density polyethylene, medium density polyethylene, low densitypolyethylene, crystalline ethylene/propylene copolymer, crystallineethylene/butene-1 copolymer, polypropylene, crystallinepropylene/ethylene copolymer, polybutylene-1, andpoly(4-methyl-pentene-1). Mixtures of two or more of those polymers orcopolymers can be used. U.S. Pat. No. '911 describes a fabricatedcomposition that comprises linear low density copolymers of ethylene andan alpha-olefin where the alpha-olefin is selected from the group whichincludes butene-1, hexene-1, methylpentene-1, and octene-1 and comprisesbetween 3 and 14 weight percent of the copolymer where the copolymer isreacted with 0.01 to 3 weight percent of an unsaturated carboxylic acidor a derivative thereof.

Additionally, U.S. Pat. No. 4,298,712 to Machonis describes adhesivecomposition which are related to the present invention. Additionalreferences include U.S. Pat. Nos. 3,658,948 to McConnell; 3,868,433 toBartz; and Japanese Patent No. 0179543. These are patents that describeinventions that fall within the general area of the present invention.Also, U.S. Pat. No. 3,896,067 to Kosaka, and U.S. Pat. No. 4,602,056 toWaniczek, as well as two Japanese Patents, Patent No. 2010107 toMitsubishi and Patent No. 1181882 to Mitsui, are of interest. The Kosakapatent discloses a hot melt adhesive containing a maleic anhydridegrafted EVA copolymer and a polyolefin. The Waniczek patent showsgrafted EVA in hot melt adhesives. The Japanese references pertain toblends of modified butene polymers with ethylene polymers and arerepresentative of the state of the art.

The present invention, directed to a hot melt adhesive made fromspecific modified ethylenic copolymer and specific butene-1 homopolymerswith or without other components, appears to lie outside the scope ofthe known art.

Hot melt adhesives with long open time good bonding to cold metals aremade of blends of a maleic anhydride modified copolymer of butene-1 andethylene, an aliphatic, substantially non-polar resin, a antioxidizingagent and, optionally, microcrystalline wax, a block copolymer andatactic polypropylene are described in U.S. Pat. No. 4,554,304. Thispatent discloses a variety of modified butene-1 homopolymers andcopolymers useful within the scope of the present invention, as well asmethods for preparing these modified butene-1 polymers. Modifiedethylene copolymer and homopolymer usable within the scope of thepresent invention are not taught in this disclosure.

The instant invention recognizes that conventional multilayer peel sealfilms or sheets are comprised of substrates and peelable sealingswherein the sealants are not hot melt type of adhesives. The presentinvention teaches a novel hot melt adhesive blend, a laminar structureand a method of making a packaging film system which is capable ofpeelability. The instant invention has, as an object, a peelable systemwhich avoids delamination between layers when the sealed layers arepulled apart. In some embodiments, a tackifying resin is added to helpbind together incompatible substrates.

It should be noted that the present invention has been developed toprovide a blend of two non-compatible polymers to form a bond with acontrollable cohesive strength.

Several terms are used throughout the specification. "Noncompatiblepolymers" are defined as polymers which, when blended or mixed, separateinto two separate phases. "Controllable Cohesive Strength" refers to anadhesive wherein the cohesive strength can be varied or controlled bychanging the ratio of noncompatible components.

SUMMARY OF THE INVENTION

In the present invention, the hot peelable melt adhesive, can compriseeither a modified butene-1 homopolymer or copolymer blended with about5% by weight to about 50% by weight of an ethylenic copolymer and asmall amount of stabilizer (up to 1 part per hundred) or alternatively,a modified ethylenic copolymer blended with about 5% by weight to about50% by weight of a butene-1 homopolymer or copolymer and a small amountof a stabilizer, (up to 1 part per hundred). A quantity of a tackifyingresin can be added to the novel blends, and the amount can be varieddepending on the other components used in the adhesive. Optionally, upto 30 phr of a wax, and/or up to 15 phr of an atactic propylenehomopolymer or copolymer can be added to the novel blend formulations.

In the present invention, a laminar structure can be made using thenovel hot melt adhesive formulations to form peelable structures orclosures. Compatible substrates of nylon, polycarbonate, stainless steeland other similar materials, as well as substrates which arenon-compatible towards the formulations could be used.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Within the scope of the present invention the term "modified" refers topolymers which have been associated, such as by intimate blending, witha small amount of maleic anhydride in amounts from 0.05 to 5% by weight.Alternatively, "modified polymers" may be polymers which have beenassociated with a quantity of peroxide, such as by blending in a tumbleror drum, to become crosslinked and then additionally blended with asmall amount of maleic anhydride. The modified polymers may be referredto herein as graft polymers.

The modified butene-1 homopolymer and copolymers are a unique group ofolefinic polymers because of their slow crystallization rates. The veryslow crystallization rate of modified butene-1 polymers, in contrast tothe crystallization rates of other polyolefin crystalline polymers suchas EVA, polyethylene and polypropylene, have been found to be beneficialin formulating the novel hot melt adhesives which have good adhesion toa variety of substrates (metals such as stainless steel and anodizedaluminum, for example).

Modified polybutylene homopolymers and copolymers useful with thepresent invention are primarily linear chain molecules with regular andspatially ordered arrangements of ethyl side groups; the groups thatresult when one butene is polymerized across the 1,2 carbon double bondalong an ethylene chain backbone. When cooled from a melt, the ethylside groups initially align in a tetragonal spatial arrangement,developing a little over one half of the ultimate crystallinity (formII) of the polymer. With time, the tetragonal crystalline phase form IItransforms into a stable hexagonal spatial arrangement with subsequentdevelopment of additional crystallinity form I. Modified butene-1copolymers can be modified butene-1 ethylene copolymers with an ethylenecomonomer content in a range of 1-30 mole percent though 11-20 molepercent is preferred.

Unmodified or "non-modified" butene-1 hompolymers and copolymers areusable within the scope of the present invention only when used inconjunction with a modified ethylene homopolymer or copolymer component.Unmodified polybutylene homopolymers are disclosed in U.S. Pat. No.3,362,940 and incorporated by reference herewith. Unmodified butene-1copolymers can comprise one or more of a variety of alpha-olefins, seefor example the butene-1 copolymers also taught in U.S. Pat. No.3,362,940. Butene-1/ethylene copolymers, with ethylene comonomer contentin the range of 11-20 mole percent are expected to be particularlyuseful in the present inventive hot melt adhesive as the ethylenecomonomer produces a lower glass transition temperature (Tg) amorphousphase, further reduces the crystallization rate of the adhesive andfurther reduces the ultimate level of crystallinity in the polymer. Thedevelopment of the inventive hot melt adhesive with these novelpeelability features can be formulated with a variety of othercomponents, such as tackifying resins, waxes, oils, stabilizers, andother additives, such as atactic polypropylene homopolymer or copolymer.

The butene-1 polymers of the present invention can be butene-1homopolymers or alternatively butene-1 copolymers with a comonomer ofpropylene, ethylene, or an alpha olefin having from 5 to 8 carbon atoms.If butene-1 copolymers are used, the comonomer mole percent ispreferably between 1 and 30 mole % based on the entire copolymer.

The modified and unmodified butene-1 homopolymers and copolymers usablewithin the scope of the present invention, can be selected from polymersin a wide range of melt flows fractional to 1000 dg/min based on ASTMD1238 condition E at 190° C. High melt flow polymers and low melt flowpolymers are contemplated as usable herein. Shell Chemical CompanyPolybutylene 0800 is considered usable herein.

Within the scope of the present invention, modified and unmodifiedethylene components are used. Modified ethylene copolymers having meltflows that range from fractional to 100 dg/min based on ASTM test D1238,condition E at 190° C. are particularly useful.

Within the scope of the present invention, the ethylenic copolymer maybe a modified or unmodified ethylene vinyl acetate copolymer (EVA), amodified or unmodified ethylene methyl acrylate copolymer (EMA), or amodified or unmodified ethylene-acrylic acid copolymer. Most preferably,ethylene vinyl acetate copolymers in either the modified or unmodifiedform, depending on which butene-1 component is selected, are consideredparticularly usable within the scope of the invention.

It is contemplated that a modified ethylene component is only usablewith an unmodified butene-1 component, and an unmodified ethylenecomponent is only usable with a modified butene-1 component in thepresent invention.

Stabilizers usable within the scope of the present invention can behindered phenols, such as Irganox 1010, made by Ciba Geigy Corporation,Ethanox 330 made by Ethyl Corporation, or phosphorus-based stablizers,such as Irgafos 168 made by Ciba Geigy Corp. Irganox 1010 is the mostpreferred stabilizer for use in this invention. The quantity ofstabilizer usable within the scope of the present invention is expressedin parts per hundred (phr) based on the total amount of the componentsin the hot melt adhesive which are expressed in weight percent. Ethanox330 is a 1,3,5,-trimethyl-2,4,6-tris[3,5-di-tert-butyl-4-hydroxy-benzyl] benzene. Irganox 1010 is usuallyreferred to as tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane. It is preferred touse about 0.3 phr of a stabilizer, although about 0.1 to about 2 phr isalso usable within the scope of the invention.

Tackifying resins usable within the scope of the present invention canbe either compatible with the modified or unmodified copolymer componentor compatible with the modified or unmodified butene-1 homopolymer orcopolymer component and generally not with both the butene and theethylene polymers. It Is necessary that the tackIfyIng resin becompatible with the modified component of the blend.

If a modified or unmodified ethylene copolymer compatible tackifyingresin is used in the present invention, it can be selected from thegroup of polar tackifier resins. Rosin esters or aliphatic hydrocarbonresins may be usable within the scope of the invention. Examples ofresins compatible with the modified or unmodified ethylene copolymerinclude, Zonester 85 (Glycerol esters of disproportionated tall oilrosin) and Zonester 100 made by Arizona Chemical Company, or Kristalex3070 (an alpha methyl styrene based resin) made by Hercules Corporation.

If a modified or unmodified butene-1 homopolymer or copolymer compatibletackifying resin is used in the present invention, it is preferred thatthe tackifying resin be non-polar, such as Regalrez 1078 (a hydrogenatedhydrocarbon resin) made by Hercules, Escorez 1304 (also a hydrocarbonresins) available from Exxon Chemical Company, Wingtack 95 (a syntheticpolyterpene resin), or Wingtack 85, all available from Goodyear Tire andRubber. Within the scope of the present invention, a member of the groupconsisting of: partially hydrogenated C₉ based hydrocarbon resins withsoftening points in a range of 70° C. to 125° C., as well as C₅ streamresins, and polyterpenes, in amounts of from about 20% by weight toabout 60% by weight and preferably 50% by weight also can beincorporated into the adhesive.

The waxes usable in the present invention can be microcrystalline waxes,though other waxes may be used. The waxes may be used in amounts up to30 phr (parts per hundred) based on the overall adhesive composition.Shellwax® 100, 300, and 500 are examples of waxes likely to be preferredfor use within the scope of the present invention. A sufficient amountof the wax, 10 to 30 phr, and preferably 20 phr, should be usable in theinvention and provide the advantage of lowering viscosity in the overalladhesive composition without substantially decreasing the servicetemperature of the adhesive.

Atactic polypropylene (such as AFAX 510 made by Hercules Inc. ofWilmington, Del.) may be added to the novel composition in amountsranging up to about 15 phr of the overall adhesive formulation. Mostpreferably, 15 phr of Afax 510 is contemplated to provide the mostadvantageous benefits such as: (1) improved processability of theoverall adhesive formula by acting as a diluent, and (2) reduced cost ofthe resulting adhesive.

The quantity of atactic polypropylene usable within the scope of thepresent invention is expressed in phr of the components of the hot meltadhesive in a manner identical to the method used for expressing thequantity of stabilizer usable within the scope of this invention.

Plasticizers, such as oils, like Shellflex® 371, can also be added tothe composition to reduce the cost of production in making the finalpeelable product. These plasticizers may also enhance processability ofthe adhesive.

The present invention includes a laminated structure wherein adhesive isused between substrates in a continuous or non-continuous manner. If theadhesive is to be applied in a continuous manner, the substrate shouldbe compatible with the major component of the adhesive. If the adhesiveis to be non-continuously applied, the substrate can be eithercompatible or non-compatible with the major component.

The laminated structure could contain one of the following as asubstrate: nylon, polyester, polyvinyl chloride (PVC), high densitypolyethylene (HDPE), polypropylene (PP), polycarbonate (PC), polystyrene(PS), polyacrylonitrile (PAN), paper or aluminum foil or poly-4-methylpentene. It is not intended that the substrate of the laminatedstructure be limited to only the above named compounds, any compoundusable as a substrate, within the scope of the present invention iscontemplated.

For modified butene-1 "rich" adhesives, (i.e., high butene-1 contentadhesives, usually with more than 50 wt % butene-1) the compatiblesubstrate would be foil, polypropylene, treated steel, aluminum, andpaper. Substrates compatible with an adhesive having a major amount ofmodified ethylene include, paper, polyester and high densitypolyethylene.

Substrates which are non-compatible with adhesives having as the majorcomponent modified polybutene include: polycarbonate, polyacrylnitrilecopolymer, poly-4-methyl pentene, nylon, polyvinyl chloride, (PVC), andhigh density polyethylene.

Substrates which are non-compatible with adhesives having as the majorcomponent, modified polyethylene include: polycarbonate,polyacrylnitrile copolymer, poly-4-methyl pentene, and polypropylene.

The addition of a tackifying resin will most likely alter the adhesiveeffect between the substrate and the adhesive.

The laminated structure can be made by coating the inventive hot meltadhesive on at least one side of a substrate. A sandwich style laminateis also contemplated within the scope of the invention.

It has been discovered that a hot melt adhesive may be made withcomponents (a) and (b) having ratios (a):(b) that range from 70:30 to30:70 percent by weight of the major component of the blend either(a)(1) modified ethylene copolymer or (2) modified butene-1 homopolymeror copolymer to (b) tackifying resin. These percentages may be alteredto be within the more preferred ratio of 60:40 to 40:60. The mostpreferred embodiment is contemplated as 50:50 (in weight percent) ofmodified butene-1 component or modified ethylene component to therespective compatible tackifying resins.

If the adhesive composition comprises additional components oftackifying resin and atactic polypropylene, wax and/or anotherstabilizer, and the composition consists of a minor amount of butene-1homopolymer or copolymer and a major amount of the modified ethylenecomponent then the composition can comprise formulations such as thoseappearing below:

(1) a formulation consisting of from about 66.6 to about 15 weightpercent of a modified ethylene copolymer, from about 5 to about 50weight percent of a butene-1 homopolymer or copolymer, up to 1 part perhundred of a stabilizer, from about 15 to about 66.5 weight percent of amodified ethylene compatible tackifying resin, up to 30 phr of a wax,and/or uP to 15 phr of atactic polypropylene, and further wherein thecomposition of tackifying resin to modified ethylene copolymer is in therange of from 30:70 to 70:30 of resin to modified ethylene copolymer.

(II) a formulation consisting of from about 57 percent by weight toabout 20 percent by weight of a modified ethylenic copolymer, from about5 percent by weight to about 50 percent by weight of a butene-1homopolymer or copolymer, up to about 1 phr of a stabilizer, from about57 percent by weight to about 20 percent by weight of a modifiedethylene compatible tackifying resin, up to 30 phr of a wa and/or up to15 phr of atactic polypropylene and further wherein the compositionratio of tackifying resin to modified ethylene copolymer is in the rangeof from 40:60 to 60:40 of resin to modified ethylene copolymer,

(III) a formulation which comprises from about 47.5 percent by weight toabout 25 percent by weight of a modified ethylenic copolymer, from about5 percent by weight to about 50 percent by weight of a butene-1homopolymer or copolymer, up to about 1 phr of a stabilizer, and fromabout 25 percent by weight to about 47.5 percent by weight of a modifiedethylene compatible tackifying resin, up to 30 phr of a wax, and/or upto 15 phr of atactic polypropylene, and further wherein the compositionof tackifying resin to modified ethylene copolymer is in a 1:1 ratio ofresin to modified ethylene copolymer.

If the adhesive composition comprises wax and additional components,such as tackifying resin, atactic polypropylene, and/or anotherstabilizer, and the composition consists of a minor amount of anethylene component, and a major amount of modified butene-1 homopolymeror copolymer, then the composition can comprise the formulations such asthose appearing below:

(IV) a formulation consisting of from about 5 percent by weight to about50 percent by weight of an ethylenic copolymer, from about 66.5 percentby weight to about 15 percent by weight of a modified butene-1homopolymer or copolymer, up to about 1 part per hundred of astabilizer, and from about 15 percent by weight to about 66.5 percent byweight of a modified butene-1 compatible tackifying resin, up to 30 phrof a wax, and/or up to 15 phr of atactic polypropylene and furtherwherein the composition of tackifying resin to modified butene-1homopolymer or copolymer is in the range from 30:70 to 70:30 of resin tomodified butene-1 homopolymer or copolymer.

(V) a formulation consisting of from about 5 percent by weight to about50 percent by weight of an ethylenic copolymer, from about 57 percent byweight to about 20 percent by weight of a modified butene-1 homopolymeror copolymer, up to about 1 part per hundred of a stabilizer, and fromabout 20 percent by weight to about 57 percent by weight of a modifiedbutene-1 compatible tackifying resin, up to 30 phr of a wax, and/or upto 15 phr of atactic polypropylene resin and further wherein thecomposition of tackifying resin to modified butene-1 homopolymer orcopolymer is in the range from 40:60 to 60:40 of resin to modifiedbutene-1 homopolymer or copolymer.

(VI) a formulation that comprises from about 5 percent by weight toabout 50 percent by weight of an ethylenic copolymer, from about 47.5percent by weight to about 25 percent by weight of a modified butene-1homopolymer or copolymer, up to about 1 phr of a stabilizer, and fromabout 25 percent by weight to about 47.5 percent by weight of themodified butene-1 compatible tackifying resin, up to 30 phr of a waxand/or up to 15 phr of atactic polypropylene, and further wherein thecomposition of tackifying resin to modified butene-1 homopolymer orcopolymer is in the ratio of 1:1 of resin to modified butene-1homopolymer or copolymer.

EXAMPLE Adhesive Preparation

Modified butene-1 or modified ethyl vinyl acetate (EVA) polymers can beprepared by functionalizing butene-1 or EVA with maleic anhydride. Themodified butene-1 polymers may be prepared by mixing polybutylenepellets with a peroxide (Lupersol 101) at 2000-10000 ppm and theappropriate amount of maleic anhydride. The mixture should be passedthrough a heated extruder. The temperature of the extruder should bechosen so as to melt the polybutylene and to cause substantiallycomplete decomposition o: the peroxide for example, heat at 200° C. andusing an rpm to obtain about a 2 minute residence time. Typically1000-4000 ppm of a peroxide (Lupersol 101) can be used with 0.1% wt to5% wt maleic anhydride.

Adhesives may be prepared using either a small Brabender compound head(approximately 50 cc capacity) or a one quart sigma blade mixer. Thetest formulations can be blended using preheated equipment (preheated to170° C.-180° C.) by introducing the polybutylene polymer, and mixing,until a soft, homogeneous mass is formed, and then gradually introducingthe remaining ingredients. Batch times can be about 20 minutes.

EXAMPLE II Adhesive Film

Thin adhesive films (125 to 200 microns) can be prepared by casting ontorelease coated polyester film (onto release coated side) using a pair ofheated nip rolls that are adjusted to produce the desired gap, (hencethe defined adhesive thickness). Preheated adhesive (at about 130° C.)can be poured onto a polyester film and hand drawn through the heatednip rolls. Alternatively, the adhesive can be poured onto the substrateand a "doctor blade" can be "drawn down" the adhesive to achieve auniform coating on the substrate. Other methods of applying hot meltadhesive can also be used. For continuous or non-continuous application,techniques such as spraying the adhesive, using hot melt guns to applyadhesive or extruding the adhesive can be used. Using the firstdescribed technique, adhesive films, 4" wide and 8" long, can beproduced with a small quantity (<60 gms) of adhesive, so that very smallquantities of adhesive can be evaluated.

Once cooled and allowed to set, these adhesives can be used to preparetest specimens. For example, Kraft paper to Kraft paper, polypropyleneto polypropylene and polyethylene to polyethylene bonds can be made bycutting adhesive squares from the polyester film, peeling them off,placing the adhesive between the paper and heat sealing with a hot barsealer (time, pressure and temperature can be adjusted). Alternately,the adhesive square or an adhesive strip may be placed on a piece ofplastic or metal substrate, melted with a heat gun (or in an oven), andthen joined under moderate contact pressure to form T-peel, lap shear orSAFT bonded substrate specimens.

TESTING METHODS

1. Adhesive Hot Melt Viscosity--Viscosities can be measured at 177° C.in a Brookfield Thermocell Viscometer with an RVT head and Number 29spindle (ASTM D3236); for low viscosity formulations, a number 27spindle can be used.

2. Peel Strength--a 25 mm×150 mm laminate sandwich can be formed withthe substrate of interest, the adhesive as the interlayer between thesubstrate surfaces. The laminate surfaces can be placed in an Instrontester, one surface in the lower jaw. The jaws can be separated at arate of 25 cm/min. Force required to peel the surfaces can be recordedcontinuously. The maximum and minimum values should be noted, as well asfailure mode, i.e., adhesive, cohesive, or a combination. This testshould approximate a peel angle of about 180° C.

Table 1 illustrates the anticipated differences between the adhesivesconsisting of a major amount of modified butene-1 component and a minoramount of ethylene component or a major amount of modified ethylenecomponent and a minor amount of butene-1 component.

                                      TABLE 1                                     __________________________________________________________________________    Hot Melt Adhesives                                                                       % wt                                                               Formulation                                                                              1  2  3  4  5  6  7  8  9  10 11 12                                __________________________________________________________________________    Butene-1 polymer.sup.(1)                                                                 85 -- 15 15 55 -- 15 15 50 -- 15 15                                Modified buene-1                                                                         -- 85 -- -- -- 55 -- -- -- 50 --                                   polymer.sup.(2)                                                               Ethylene polymer.sup.(3)                                                                 15 15 85 -- 15 15 55 -- 15 15 50 --                                Modified Ethylene                                                                        -- -- -- 85 -- -- -- 55 -- -- -- 50                                polymer.sup.(4)                                                               Tackifying Resin.sup.(5)                                                                 -- -- -- -- 30 30 -- -- 25 25 -- --                                Tackifying Resin .sup.(6)                                                                -- -- -- -- -- -- 30 30 -- -- 25 25                                Wax.sup.(7)                                                                              -- -- -- -- -- -- -- -- 10 10 10 10                                Stabilizer.sup.(8)                                                                       0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                          phr                                                                              phr                                                                              phr                                                                              phr                                                                              phr                                                                              phr                                                                              phr                                                                              phr                                                                              phr                                                                              phr                                                                              phr                                                                              phr                               TESTS                                                                         Adhesion to substrates                                                        Aluminum Foil                                                                            N  Y  N  Y  N  Y  N  Y  N  Y  N  Y                                 Nylon      N  Y  N  Y  N  Y  N  Y  N  Y  N  Y                                 __________________________________________________________________________     .sup.(1) Butene-1 polymer is a copolymer of butene1 and ethylene known as     Duraflex ® Polybutylene 8910 available from Shell Chemical Company.       .sup.(2) Modified butene1 polymer is polybutylene 8910 grafted with 1.0%      wt maleic anhydride.                                                          .sup.(3) Ethylene copolymer is ethylene vinyl acetate (EVA) Ultrathene        ® 64904 available from U.S. Industrial Co.                                .sup.(4) Modified Ethylene Copolymer is EVA (64904) grafted with 1.0% wt      maleic anhydride.                                                             .sup.(5) The tackifying resin is Zonester 85.                                 .sup.(7) The wax is Shellwax 400.                                             .sup.(8) The stabilizer is Irganox 1010, and is a hindered phenol.            N = no bond; Y = yes, there is bond.                                     

What is claimed is:
 1. A hot melt adhesive capable of peelability,consisting of a major amount of a modified ethylene copolymer,comprising:from about 50 percent by weight to about 95 percent by weightof a modified ethylenic copolymer selected from the group: maleatedethylene methyl acrylate copolymer, and maleated ethylene acrylic acidcopolymer; from about 50 percent by weight to about 5 percent by weightof a butene-1 homopolymer or copolymer; and up to about 1 part perhundred (phr) of a stabilizer.
 2. The hot melt adhesive of claim 1,comprising:from about 60 percent by weight to about 80 percent by weightof said modified ethylenic copolymer; from about 40 percent by weight toabout 20 percent by weight of said butene-1 homopolymer or copolymer;and up to about 1 part per hundred (phr) of said stabilizer.
 3. A hotmelt adhesive capable of peelability, comprising:from about 66.5 percentby weight to about 15 percent by weight of a modified ethyleniccopolymer selected from the group: maleated ethylene methyl acrylatecopolymer, and maleated ethylene acrylic acid copolymer; from about 5percent by weight to about 50 percent by weight of a butene-1homopolymer or copolymer; up to about 1 phr of a stabilizer; and fromabout 15 percent by weight to about 66.5 percent by weight of a modifiedethylene copolymer compatible tackifying resin; and further wherein thecomposition of said tackifying resin to said modified ethylene copolymeris in the range of from 30:70 to 70:30 of said resin to said modifiedethylene copolymer.
 4. The hot melt adhesive of claim 3, comprising:fromabout 57 percent by weight to about 20 percent by weight of saidmodified ethylenic copolymer; from about 5 percent by weight to about 50percent by weight of said butene-1 homopolymer or copolymer; up to about1 phr of said stabilizer; and from about 20 percent by weight to about57 percent by weight of said tackifying resin; and further wherein thecomposition ratio of said tackifying resin to said modified ethylenecopolymer is in the range of from 40:60 to 60:40 of said resin to saidmodified ethylene copolymer.
 5. The hot melt adhesive of claim 3,comprising:from about 47.5 percent by weight to about 25 percent byweight of said modified ethylenic copolymer; from about 5 percent byweight to about 50 percent by weight of said butene-1 homopolymer orcopolymer; up to about 1 phr of said stabilizer; and from about 25percent by weight to about 47.5 percent by weight of said tackifyingresin; and further wherein the composition of said tackifying resin tosaid modified ethylene copolymer is a 1:1 ratio of said resin to saidmodified ethylene copolymer.